I thought I posted this last night but couldn’t find it this am – my apologies if this is a double post.

I’m seeking advice on heating/cooling system for the house we’re building next year. I’m trying to form a big-picture idea of what we want to do before I try for quotes with hvac companies.

Size:
   1800 sq ft – first floor, living space for us
   1800 sq ft – insulated basement/slab, storage (but all houses have them in our area)
     600 sq ft – sec. floor, for family guests staying for wks at a time
   Attached two-car garage – unconditioned

Walls: drywall (gaskets), 2x6 16 o.c. w/ blown material tbd, OSB (poss. taped), 1.5” iso ext. foam (taped), VP and/or rain barrier (not sure yet), vinyl siding
Roof: targeting R40, not sure what material yet, light colored metal roof
Location: South-central PA

My Thoughts/Questions so far:

Geo. HP is not in the budget (we’re spending it on the envelope). No natural gas and I don’t prefer a tank, so we’re looking at all electric (heat pump?).

If I have an insulated door to upstairs (guest area), can I just heat/cool it very, very minimally unless occupied – or is that a drag on heat/cooling for the occupied first floor?

If I have an insulated door to the basement (storage), can I not actively heat/cool it at all even though it is in the building envelope?

My brief experience so far seems that hvac folks want to put in a unit to keep the entire house cool (70 deg) on the hottest day of the year. We never set our A/C to 70! Try somewhere between 75 and 78. And in the winter we’re OK with 68. I’m concerned about being forced into more equipment than I need or want. I know about manual J calculations (don’t personally know how to do them!) – but ya’ know what – it seems in practice many contractors don’t do those calculations and size on more general rules.

What are your thoughts/experiences with a mini-split system? I’m thinking I could get a smaller unit and good zoning capability. But they’re not typical in our area (and I think are considered “low end”, like it belongs in a cheap hotel.) I don’t care too much about perceptions, but want to get quality equipment that won’t be loud in the room.

Thanks much for your help.

I would find a local contractor that uses a computerized manual J like Elite or Wrightsoft and be willing to pay a few bucks for someone to take the time to do it right, give you a printed out report and consult you on options. Manual D, S, and T are also important in the designing stages of HVAC. The calculations aren't rocket science but I will warn you of the learning curve. Proper sizing is like the foundation of a building, if it's wrong the building is doomed. I would need to see your floor plan before commenting on equipment type but I have reservations about mini splits for the whole house and I never do more than 3 zones per system (prefer just 2 per system).

If you increased your insulation thickness by 4 inches, used triple glazed windows and air tightened well your heating-cooling system could be 5 times smaller.

You can buy a personal license for HVAC-Calc (http://www.hvaccomputer.com/) for $49 and do your own heating/cooling load calculation. That's what I did when building my energy efficient house and it worked out nicely. Having some experience with heating and cooling standard construction homes, I was surprised at how little heating and cooling capacity was needed for my ICF house. I had trouble finding a boiler small enough to match the calculated load, and my 1-1/2 ton central A/C, the smallest I could find, is too large for efficient dehumidification purposes. The house is a 2200 sf ranch with a full (heated) basement. The boiler is a modulating type (16-46 BTUH) which also provides domestic hot water. I also use mechanical ventilation with heat recovery (HRV). My measured energy efficiency is just under 2 BTU/sf/HDD.

BabyBldr: you will need a ventilation system to distribute fresh air and at that point, you might as well have it distribute heat and cooling too.

Thank you all for your input.

Jonr, I agree with you that some type of ventilation system is needed, and with that you get the duct work. But I’m not sure how a ducted system works if ~600 sq ft is used only 15 wks a year or so and ~1800 sq ft (first floor) is used full-time. Is that one duct systems with dampers? Two entirely separate systems? Or do you just go ahead and fully heat/cool the entire house?

Clark, thanks for the tip on the software. I looked at some of their instructional videos and will definitely buy and use the software to experiment. Maybe it will shed some light how separate areas of a house (zones?) are best handled. Or at least give me some data I can share with an HVAC company and see what they would recommend. At least then I’ll know each company is making a recommendation for the same set of performance data.

Thanks again, I think this info is really helpful.

Posted By BabyBldr on 30 Nov 2010 01:48 PM
Thank you all for your input.

Jonr, I agree with you that some type of ventilation system is needed, and with that you get the duct work. But I’m not sure how a ducted system works if ~600 sq ft is used only 15 wks a year or so and ~1800 sq ft (first floor) is used full-time. Is that one duct systems with dampers? Two entirely separate systems? Or do you just go ahead and fully heat/cool the entire house?

Clark, thanks for the tip on the software. I looked at some of their instructional videos and will definitely buy and use the software to experiment. Maybe it will shed some light how separate areas of a house (zones?) are best handled. Or at least give me some data I can share with an HVAC company and see what they would recommend. At least then I’ll know each company is making a recommendation for the same set of performance data.

Thanks again, I think this info is really helpful.

forced air systems can be zoned - requires some add on's, but not an entrely different system.  When we built, we were told that to add zoning control for the basement would be an extra $2000.  Not sure how well that number holds up, but that was what we were hearing..

In my previous home, which was 2-story, the first and second floors were separate zones for both heating and cooling. The 2nd floor represented a far less heating load/sf and a far greater cooling load/sf than the 1st floor. Each floor had its own furnace and A/C sized to their respective loads. Being of conventional construction (i.e, leaky), supplementary ventilation was not called for. If mechanical ventilation had been required, I would have installed two HRVs, especially if I wanted to close off the 2nd floor for periods of time. The 2nd floor HRV would have a smaller CFM rating than the main level. Depending on where you live, an ERV could be more cost effective. A livable basement should also be a separate zone, IMO. In my new house, the basement level zone is radiant hot water. It was not very expensive to lay the PEX tubing down before the basement floor was poured, so I did, and am very happy for it. Forced air supply ducts in the ceiling of a basement are not nearly as effective as an hydronic system for obtaining a comfortable basement living space. It's good that you are planning all this out in advance. I'm sure you will be much more pleased with the final outcome.

Posted By BabyBldr on 30 Nov 2010 01:48 PM
Is that one duct systems with dampers? Two entirely separate systems? Or do you just go ahead and fully heat/cool the entire house?

Could be any one of the three. A zoned system is basically an auto damper for a trunkline that could serve whatever you want. A seperate thermostat would control each zone and all zones are fed from the plenum off one furnace typically unless you have some specialty requirements, duct restrictions; huge sq footage or other possible situations where multiple zones on one furnace wouldn't work.

Call me difficult but I think the point of hvac should be comfort, and I am not sure you'll get it with a heat pump in Pa. They're golden at 40 degrees and above, but they shift in and out of defrost cycle near freezing or below and stop working at 10 degrees or so. You'll save money but you and family may complain, as my wife did for 20 years -- in a warmer climate -- that the heat pump made her feel colder. She was often right. Its output was hot enough on cold days to keep the house warm but not sufficient to overcome forced air's wind chill factor. And good luck reheating that guest area during a cold snap. (I'd consider electric radiant in the ceiling as the fastest way to bring bedding up to tolerable temperatures. Strip back the covers in any case.)
There are two economical, all-electric approaches to hydronic heat short of geo: an air-to-water heat pump or resistance coils at offpeak pricing. Ask your utility about offpeak pricing and grants. In either case I'd couple the heat to a sizable storage tank. The heat pump would store heat during the day, operating under generally favorable conditions in Lancaster Co. The off-peak system would store heat at night. The tank would carry the house for the rest of the day. You'd want in floor radiant or base boards that work at low temperatures to increase your storage capacity. 500 gallons at 140 degrees, for example, would give you 120,000 btus if your heating system still worked at 110 degrees. As a plus, in floor radiant is very, very comfortable. As a double plus, integrating solar hot water and DHW into the buffer tank is quite easy.
The minuses? No AC at this point without installing forced air anyway, altho split minis are a good solution. And there are few residential air to water heat pumps sold in the US. One attractive candidate is Daikin's Altherma. Google it and be impressed. In Europe, it sells for about half what a comparable geo system would cost. Sven at SSTS can explain tanks. SSTS is nearby in Mechanicsburg. http://www.stsscoinc.com/Products.aspx
This will take some figuring, but if your house doesn't need much hvac and you add the pieces as you can afford them, the capital outlay and payback could be manageable. Consider a heat pump swimming pool heater as a cheapo place holder until Daikin gets some competition. Gotta say I'd pay extra to avoid forced air.

Properly designed, a heat pump system should never be uncomfortable - but it may use aux heat more than you would like.